Analytical instrumentation used to determine chemical composition of samples commonly utilizes injection, switching and selector valves to perform routine fluid switching and injection of samples into pressurized fluid streams. These valves direct the movement or flow of fluid into and out of a number of components. Rotary shear valves are commonly used to direct fluid flow in such applications.
A common rotary valve 7 having a conventional design is shown in FIG. 1. A stator 13 having an outer stator face 13a and an inner stator face 13b is fixed to an actuator unit 17 by mechanical means. A rotor 9 is installed on a rotary shaft 16 that is rotated to a designated angle by the actuator unit 17. The rotor 9 has a rotor surface 9a disposed against the inner stator face 13b of the stator 13, as shown.
Referring to FIG. 2, fluid ports 1-6, respectively, in the outer stator face 13a are disposed in fluid communication with respective fluid orifices (not illustrated) on the inner stator face 13b. The rotor surface 9a of the rotor 9 may be spring-loaded against the inner stator face 13b to provide a constant force which imparts a fluid-tight seal between the rotor surface 9a and the inner stator face 13b. The rotor 9 also allows for rotary motion around the valve's central axis to direct flow of fluid through rotor grooves 10, 11 and 12, respectively, fabricated into the rotor surface 9a. The rotor grooves 10, 11, 12 are disposed in fluid communication with the fluid orifices (not illustrated) on the stator face 13b. The design and complexity of the rotor grooves 10, 11, 12 can allow for many unique connections between the fluid orifices in the stator face 13b to facilitate advantageous fluidic functions.
An example of a common rotary valve is the Cadence Fluidics UBX-1701-0206-0001. This valve is designed for two positions with position one shown in FIG. 2 and position two shown in FIG. 3. The valve has two fluid ports: fluid port 2 allows flow from a liquid supply, such as a chromatographic pump (not illustrated), and a second fluid port 5, which is adapted to receive a fluid sample from a sample syringe (not illustrated). A sample loop 8 may be connected to fluid port 1 and to fluid port 4. Fluid port 6 is an outlet port, or waste port. Fluid port 3 is also an outlet port, and in this example, is connected to a chromatography column.
In FIGS. 1 & 2, the rotor 9 is disc-shaped and has the rotor grooves 10, 11, 12. When the rotor 9 is rotated around its center axis, the rotor grooves 10, 11, 12 align with the fluid orifices in the inner stator face 13b to allow for a change in fluidic pathways. FIG. 2 shows position 1 due to the angular position of the rotor 9 in relation to the stator 13. Two fluidic functions are performed in position 1. The first is connection of the pump to fluid port 2, which is disposed in fluid communication with the chromatography column at fluid port 3 through the rotor groove 12. The second function is connection of the syringe to fluid port 5, which is disposed in fluid communication with a first end of the sample loop 8 through the rotor groove 11 and the fluid port 4. Fluid port 1 is disposed in fluid communication with a second end of the sample loop 8 and also to the rotor groove 10 and the fluid port 6, which is connected to a waste line (not illustrated). This function allows filling of the sample loop 8 by the syringe, with the excess fluid from the syringe going to waste.
FIG. 3 shows the configuration of the rotor grooves 10, 11, 12 in position 2 due to angular rotation of the rotor 9 in relation to the stator 13. This valve position allows two functions. The first function is that the pump connected to the fluid port 2 is now disposed in fluid communication with the chromatography column at the fluid port 3 through the rotor groove 10, the fluid port 1, the sample loop 8, the fluid port 4 and the rotor groove 12. This configuration allows for the sample in the sample loop 8 to be introduced by the pump into the chromatography column. The second function is that the syringe connected to the fluid port 6 is now in fluid communication with the waste line at the fluid port 5 through the rotor groove 11. This function allows excess sample to be pushed out of the syringe, and even refilled with sample.
One feature that needs to be noted is that during load and inject, as shown in FIGS. 2 and 3, the valve 7 rotates to bring the pump in fluid communication with the sample loop 8 and the chromatography column in fluid communication with the opposite end of the sample loop 8. During this injection, it is advantageous to not cross any other orifices, hence communicating only with desired orifices and corresponding fluid ports on the outer stator face 13a. If fluid communication is enabled by the rotor grooves 10, 11, 12 to waste line during the move from load to inject as an example, some of the sample could be lost by moving down these unintended passages as they are passed over on the way to the injection flow path of FIG. 3. Adding multiple modes to the valve 7 can result in less than ideal fluid communications to occur that can result in pressure spikes, pressure drops, contamination and sample loss.
A common rotary valve 7 performs routine sample introduction into a chromatographic system. There is only one mode of sample introduction, that being by the syringe, either manually or automated. In some applications other modes of sample introduction may be desired, and these usually require a different valve to be used. A valve that could perform multiple modes of sample introduction would be advantageous in chromatography applications.